panel_hostname redirects to subdomain and not ACP

Hey guys,

I've had set up "admin.domain.com" as my panel_hostname but it redirects to a subdomain instead of the ACP.

Just now I've changed it to "acp.domain.com" but it still keeps redirecting to a subdomain.

Also I get a "ERR_SSL_PROTOCOL_ERROR" when I try to access it via the port :8080 because I have SSL enabled by LetsEncrypt.
All other sites work fine.

I'm using i-MSCP 1.3.16